High frequency apparatus



Nov. 13, 1962 A. ALFORD 3,064,212

HIGH FREQUENCY APPARATUS 7 Filed Dec. 18, 1959 2 Sheets-Sheet 1 IN V EN TOR.

ANDREW ALFORD 1 WWW W ATTORNEYS Nov. 13, 1962 A. ALFORD 3,064,212

HIGH FREQUENCY APPARATUS Filed Dec. 18, 1959 V 2 Sheets-Sheet 2 SOURCE LBALUN H LOAD FIG.3

R-F SOURCE INVEN TOR.

ANDREW ALFORD W WWW ATTORNEYS United States Patent Gfiice 3,064,212 Patented Nov. 13, 1962 3,064,212 HIGH FREQUENCY APPARATUS Andrew Alford, 299 Atlantic Ave., Winchester, Mass. Filed Dec. 18, 1959, Ser. No. 860,454 6 Claims. (Cl. 3337) The present invention relates in general to high frequency apparatus and more particularly concerns a novel device for selectively controlling the flow of high frequency energy at high power levels to different outputs. The invention also comprehends the provision of apparatus for delivering energy to a pair of loads in a prescribed relative amplitude ratio with a controllable relative phase. In a specific application of the invention, equal amounts of high frequency energy at high power levels are coupled to a pair of antennas with the relative phase displacement between the two signals applied to the antennas being continuously van'ed through a range of 360 electrical degrees to effectively scan a predetermined sector.

Numerous techniques are known for scanning a predetermined sector of space with a beam of electromagnetic energy. For example in many radar systems scanning is accomplished by physically rotating the entire antenna assembly. This technique has a number of disadvantages. The high inertia of the rotating assembly limits the maximum scanning rate and requires a driving motor of considerable horsepower rating. In addition, expensive and rugged mounting assemblies are required which must be maintained in relatively precise alignment if the electrical characteristics of the rotary joint are to remain undisturbed to permit efiicient transfer of energy to the antenna. This is especially important when high power levels are transmitted because of a slight deviation from perfect concentricity may result in exceeding the breakdown potential, causing sparking.

Electromechanical techniques for scanning with stationary antennas are also well-known in the art. For example, capacitive goniometers are regularly employed in omnirange systems to establish a rotating figure-ofeight pattern. However, the usefulness of this goniometer is restricted to low power levels at frequencies below UHF (300 me.)

It is an important object of the present invention to provide apparatus for selectively controlling the transfer of high frequency energy at high power levels and UHF, SI-IF and higher VHF frequencies.

It is another object of the invention to provide means for efficiently transfering high frequency energy at high power levels to a pair of antennas while controlling the relative phase shift between the signals applied to the two antennas.

It is still another object of the invention to provide a structure for selectively controlling the transfer of power by rotating an element of relatively low inertia so arranged that the impedance presented by the device to external circuits is nearly independent of rotation.

It is a further object of the invention to provide a structure in accordance with the preceding object capable of controlling the transfer of high frequency energy at high power levels while minimizing undesired radiation from the device.

According to the invention, conducting means define a cylindrical cavity. Rotatable means within said cavity cooperate with the latter conducting means for establishing oppositely phased electric fields in adjacent sections of the cavity whose orientation is controlled by the angular orientation of the rotatable means about the cavity axis. A plurality of terminals pass through and are insulatedly separated from the cavity-defining conducting means. A like number of means insulatedly separated from but in fixed relation to the cavity-defining conducting means couple energy in the cavity to respective ones of the terminals.

In a preferred embodiment of the invention, the means within the cavity relatively rotatable with respect to the cavity axis comprises a hollow conducting tube coaxial about the cavity axis formed with opposed longitudinal slots extending for nearly the length of the cavity. An inner conductor extends along the cavity axis inside of the tube for about half the length of the cavity axis and is connected at one end to a point on the surface of the tube midway between the longitudinal slots and the end faces of the cavity. The terminals are preferably in space quadrature about the cavity axis in a plane midway between the end faces. Energy applied at one end of the cavity between the inner conductor and the hollow slotted conducting tube is delivered to the four terminals in magnitudes related to the angular orientation of the diameter passing through the longitudinal slots with respect to a diameter passing through an opposed pair of diametrically opposite terminals. When the two latter diameters coincide, the opposed pair of terminals receive essentially no energy. When said diameters are in space quadrature, the associated pair of terminals receive maximum energy.

The structure described immediately above functions to effectively provide first and second balanced signals from the respective pairs of opposed terminals which may have a modulation envelope in time quadrature by rotating the hollow tube at constant rotational velocity. These signals are converted by means of two baluns into unbalanced signals. One of the two resulting signals is then delayed by a quarter period and then both signals are applied to the side terminals of a hybrid. A pair of antennas, or other suitable loads, are coupled to the series feed input and parallel feed input, respectively, of the hybrid so that the loads receive equal amounts of energy but in relative phase determined by the contemporaneous amplitude of the two unbalanced signals applied to the hybrid side terminals.

As is well-known in the art, a hybrid has the properties that if its series feed input and shunt feed input are terminated in matched impedances, energy applied to each side terminal from a source presenting the hybrid characteristic impedance to that terminal is equally divided between the shunt and series feed inputs.

Numerous other features, objects and advantages of the invention will become apparent from the following specification when read in connection with the accompanying drawing in which:

FIG. 1 is a perspective view of a structure for selectively transferring power according to the invention with port1ons cut away to better illustrate certain constructional details;

FIG. 2 is a diagrammatic representation of a plan view generally through the mid-section of the structure shown in FIG. 1 helpful in understanding the principles of the invention;

FIG. 3 is a schematic representation of a system for converting the outputs from the structure diagrammatically represented in FIG. 2 to a pair of unbalanced signals; and

FlG. 4 illustrates an exemplary embodiment of a system according to the invention for energizing a pair of loads with equal amounts of energy of controlled relative phase.

With reference now to the drawing and more particularly FIG. 1 thereof, there is illustrated a perspective view of a structure according to the invention for selectively transmitting power from a translating device 11 through a coaxial transmission line having a center conductor 24 separated from an outer conductor 23 by means including insulating spacer 25 and to a first pair of diametrically opposed coaxial terminals 12 and 13 and to another pair of diametrically opposed terminal pairs 14 and 15 (FIG. 2). The opposed terminal pairs 14, 15 are not shown in FIG. 1 toavoid obscuring details of the internal structure. A conducting casing 16 defines a hollow cylindrical cavity having opposed conducting end faces 17 and 18, respectively. The metal faces 17 and 18 are formed with centrally located openings for accommodating ball, roller or other bearings 21 and 22 diagrammatically represented.

Bearings 21-and 22 rotatably' support a hollow conducting tube 23 coaxial about the cavity axis. An inner conductor 24 is coaxially located within tube 23 along the cavity axis and supported by suitable insulating spacers such as insulator'25.

The translating device 11 may be a conventional contac'ting or non-contacting R.-F. rotary joint. For example, a sleeve coupler comprising two spaced sections having inner and outer conductors in overlapping relationship for a quarter wavelength is satisfactory.

The other end 27 of inner conductor 24 is connected to the hollow conducting tube 23 by a metal block 28, made preferablyin the form of a small cylinder whose axis is at right angles to the inner conductor 24 and the inner surface of the conducting tube 23. It is preferable that the connecting block 28 be located midway between end faces 17 and 18. The hollow conducting tube 23 is formed with a pair of diametrically opposed longitudinal slots 31 and 32 extending for nearly the length of the cavity.

Referring to FIG. 2, there is shown'a sectional view through section 2-2 of FIG. 1 to illustrate the geometrical relationship among the different conductors and what is believed to be a typical field configuration in that section. All four circumferentially-spaced coaxial terminal pairs 1215-are'shown arranged in space quadrature. The center conductors 33-36 of terminal pairs 12-15, respectively, are shown connected to the metal conducting plates 4144, respectively, the latter plates being curved away from the cavity axis. Plates 41 and 42 are also visible in FIG. 1 and are shown to extend lengthwise generally parallel to the surface of conducting tube 23.

Means, such as insulating support members 45, maintain the conducting plates 41-44 insulatedly separated from but in fixed relationship 'to'the conductive casing 16.

'The four coaxial terminal pairs'1215 may be formed by conventional coaxial receptacles. Alternatively, coaxial transmission lines may be directly connected generally as shown by drilling a hole in the conductive casing 16,- passing the center conductor through this hole and soldering it to the associated conducting plate, and soldering'the coaxial cable shield around the opening to the conductive casing 16. This mode of connection may be desirable in sometypes of installations;

The metal conducting plates 41-44are preferably made about-half as long as the cavity length with the long dimensions parallel to the cavity axis and curved somewhat as shown with the convex sides facing the hollow conducting tube 23.

With theupper and lower halves of conductor 23 positive and negative as shown in FIG. 2 in the plane of section 22, the electric field configuration is believed to be generally as indicated by the arrowed lines drawn between conductor 23 and cavity '16. In theupper section,

the field is directed radially outward from the cavity axis In the lower section, the field is directed radially inward from the cavity axis.- 7

When conductors 41-44 are inserted in this field configuration, the following effects are believed to occur.

Conductors 43 and 44 are arranged with eachhaving its upper half in a field oriented toward one side and its lower half in a field of substantially the same intensity oriented to the opposite side. Since plates 43 and 44 are conductors, they establish a boundary condition requirement which seems to be capable of being met only if the potential on these plates is zero; that is, ground potential. On the other hand, conducting plates 41 and 42 are nearly normal to the respective fields inthe upper and lower Referring to FIG. 3, there is shown a schematic representation of a system utilizing the structure of FIGS. 1 and '2 in cooperation with a pair of baluns 46 and 47 to provide a pair of unbalanced signals on transmission lines 51 and 52 for energizing loads 53 and 54 respectively. 1 Transmission lines 55 and 56 couple the outputs from the diametrically opposite coaxial terminal pairs 12 and 13 to the inputs of balun 47. Coaxial transmission lines 57 and 58 couple the outputs of coaxial terminal pairs 14'and 15 to the inputs of balun 46, respectively. An R.-F.

source 61 delivers high frequency energy, to inputterminal 11.

When loads 53 and 54 are of equal impedance and approximately matched to the characteristic impedance of 1 lines 51 and 52, respectively, thefollowingphenomena are observed. As conducting tube23 is turned about the cavity axis, the amplitude of the R.-F. signal delivered to load 54 increases and decreases approximately in proportion to the sign of the angle ofrotation of .the hollow conducting tube 23. Similarly, the amplitude of the r R.-F. signal delivered by line 51 to load 53 .varies approximately as the cosine of the angle of rotationof conducting tube 23. it has been discovered that. the degree of deviation from a perfect sinusoidal relationship is a function of 1 the shape of the plates 4144 and their distance from the conducting tube 23. With concave plates half as long'as the longitudinal'slots and placed half the radius of the cavity away from the cavity axis, the maximum deviation from perfect sinusoidality is within 5% of the peak sinusoidal amplitude variation. Thus, the novel device functions as a high power switch, for by turning the hollow conducting tube 23 through mechanical degrees, delivery of power may be transferred from load 53 to load 54. A switch of.this kind is advantageous because it may be operated under power without danger of arcing. The switch may, therefore, be useful in a PAR system to change between energizing azimuth and elevation antennas.

Since the rotatable tube comprises thin conducting Walls close to the axis of rotation, the inertia of the movable assembly is low. This enhances the rise time transient response characteristics of the switch and results in a requirement for a relatively low capacity rotative power source.

Referringagain to FIG. 2, it is seen that the slots 31 and 32 are diametrically opposite. When the diameter passing through the slots coincides with the common axis of an opposed pair of coaxial terminal pairs, such terminal pairs receive substantially no energy while the remaining pair of opposed coaxial terminal pairs in space quadrature are maximally energized.

Referring to FIG. 4, there is shown still another system according to the invention which permits loads 61 and 62. connected to the parallel feed and series feed inputs re-- spectively of-a hybrid 63 to be energized "withequal amounts of energy but of a controlled relative phase. The

portion enclosed in broken linesis essentially the system hybrid 63 receives power arriving via line 52 delayed by 90 with respect to the power delivered by line 51. The opposite load 62 connected to the series feed input of the hybrid receives power from line 52 delayed not only by the 90 but also by an additional 180 with respect to the power arriving from line 51. As a result, the vector relationships 65 and 66 occur for loads 61 and 62, respectively, so that the resultant vector represents the relative phase between energy applied to loads 61 and 62.

As previously stated, when hollow tube 23 is rotated about its axis, the amplitude of the R.-F. voltages delivered by lines 51 and 52 vary respectively as the sine and the cosine of the angle of rotation of hollow tube 23. As may be seen from the vector diagram 65 and 66, the vectors representing the resultant voltages delivered to loads 61 and 62 will remain equal and substantially constant in magnitude but will rotate in opposite directions with respect to each other. That is, one will rotate in the same direction as the hollow conducting tube 23 is rotated while the other will rotate in the opposite direction. If loads 61 and 62 are two antennas spaced at some distance from each other, the beam of the array consisting of the two antennas can be rotated through 360 by rotating the conducting tube 23.

There has been described novel high frequency apparatus for selectively controlling the flow of high frequency energy and a novel exemplary system capable of incorporating the novel power transfer device for applying equal amounts of energy to a pair of loads while controlling the relative phase therebetween. High power levels may be accommodated while continuously varying output signal characteristics by rotating a low inertia device so that relatively small amounts of mechanical driving power are required.

The low inertia is advantageous when rapid switching is required.

It is apparent that those skilled in the art may now make numerous modifications of and departures from the specific embodiments described herein without departing from the inventive concepts. Consequently, the invention is to :be construed as limited only by the spirit and scope of the appended claims.

What is claimed is:

1. High frequency apparatus comprising, conducting means defining a cylindrical cavity having opposed conducting end faces, hollow conducting tube formed with opposed lon itudinal slots, means for rotatably supporting said tube concentric about the cavity axis with said longitudinal slots within said cavity, an inner conductor extending into said conducting tube along said axis through one of said end faces for less than the length of said cavity, the end of said inner conductor inside said cavity being connected to said conducting tube at a point between said slots, means for insulatedly separating the remaining portion of said inner conductor from said one end face, and said conducting tube, said conducting means defining said cavity being formed with a plurality of openings circumferentially spaced about said axis, a like plurality of conducting means within said cavity and outside of said hollow conducting tube insulatedly separated from the latter and said conducting means defining said cavity, and a like plurality of center conductors connected from a respective one of said conducting means within said cavity through and insulatedly separated from a respective one of said circumferentially spaced openings.

2. High frequency apparatus in accordance with claim 1 wherein the length of said cavity is approximately a half wavelength at a predetermined high frequency, said inner conductor extends into said cavity for approximately onefourth of said wavelength and is connected to a point approximately midway between said slots and approximately midway between said conducting end faces, and said circumferentially spaced openings are in space quadrature in a plane approximately midway between said end faces, said center conductors comprising four coaxial terminal pairs in space quadrature, said inner conductor comprising an input coaxial terminal pair surrounding said cavity aXIS.

3. High frequency apparatus in accordance with claim 2 and further comprising, means for applying energy of said high frequency to said input coaxial terminal pair to establish an electric field within said cavity whose orientation is controlled by the angular position of said rotatably supported hollow conducting tube, and means for combining energy transmitted through said four coaxial terminal pairs to derive first and second output signals of substantially constant amplitude whose relative phase is related to the angular orientation of said hollow conducting tube about said cavity axis.

4. High frequency apparatus in accordance with claim 3 wherein said energy combining means comprises, first and second means for combining the energy delivered by a respective opposed pair of said ciroumferentially displaced coaxial terminal pairs to provide first and second unbalanced signals respectively.

5. High frequency apparatus in accordance with claim 4 and further comprising, a hybrid junction having a series feed input, a parallel feed input and a pair of side terminals, means for imparting a relative phase displacement of substantially ninety electrical degrees between said first and second unbalanced signals to provide a pair of signals in time quadrature, means for coupling the said pair of signals in time quadrature to respective ones of said side terminals, and a pair of loads respectively coupled to said series feed input and said shunt feed input.

6. High frequency apparatus comprising, conducting means defining a cylindrical cavity, means within said cavity relatively rotatable with respect to the cavity axis for establishing oppositely phased electric fields in adjacent sections of said cavity angularly spaced about the cavity axis with one of said fields directed generally radially inward while the other of said fields is directed generally radially outward from said cavity axis and whose angular orientation about said cavity axis is controlled by the angular orientation of said rotatable means about the axis of said cavity, a plurality of terminals passing through and insulatedly separated from said cavity defining conducting means, and a like plurality of means insulatedly separated from but in fixed relation to the latter conducting means for coupling energy in said cavity to respective ones of said terminals.

References Cited in the file of this patent UNITED STATES PATENTS 2,196,673 Gutzmann Apr. 9, 1940 2,439,255 Longfellow Apr. 6, 1948 2,555,154 Raymond May 29, 1951 2,769,146 Alford Oct. 30, 1956 2,831,169 Casal Apr. 15, 1958 

